1. Field of the Invention
The present invention relates generally to stents for body lumens. More specifically, the present invention relates to stents created in situ within a body lumen through the conversion of a fluent material to a non-fluent material where the fluent material is delivered to the body lumen in a fluent state.
2. Discussion of Related Art
Angioplasty is a procedure for treating blood vessels or arteries which have become narrowed by plaque deposits. Typically, a catheter comprising an inflatable balloon is advanced along a path of travel through the artery to a narrowed or stenosed region. The balloon is inflated at the stenosed region of the artery causing it to be expanded. The balloon is then deflated and withdrawn.
The effect of inflating a balloon against a narrowed arterial wall typically produces injuries. When an angioplasty balloon is inflated, the single layer of cells constituting the endothelial lining typically are torn away. Also, the inflation of the angioplasty balloon may induce fissures or other injuries to the arterial wall. The loss of endothelial cells and injury to the arterial wall create an irregular surface. Such tears and unconformities in the arterial wall, along with the loss of the endothelial layer, activate the coagulation system. This in turn may form sites for promoting the growth of blood clots, which then again occlude and narrow the artery.
Conventional cardiology procedures include the introduction of a stent to a target site in a blood vessel or artery after balloon angioplasty has been performed to provide structural support to the vessel.
Conventional stents typically are fabricated of metal or plastic and include a central lumen to permit the flow of blood through the blood vessel. The metal or plastic composition is necessary to provide sufficient rigidity to hold the blood vessel or artery open. Conventional stents are fabricated outside of the body and introduced into the blood vessel or artery on the outside of a catheter. The stent is then advanced along a path of travel to the point of intervention. As the stent is advanced through the blood vessel or artery, the inherent stiffness and pre-formed configuration of the stent often causes trauma to the vascular wall and the endothelial lining.
Devices have been developed for delivering a polymeric preformed stent on the outside of a catheter which is expanded and hardened within the vessel lumen. See U.S. Pat. Nos. 5,100,429, 5,334,201, 5,344,444, 5,443,495, 5,464,419, 5,529,653, 5,599,307, 5,634,946 and 5,653,736.
Several devices have also been developed for applying a fluent material to the surface of a vessel lumen. See U.S. Pat. Nos. 5,634,946, 5,612,050, 5,599,307, 5,575,815, 5,213,580, 5,328,471, 5,256,141, 5,092,841, and WO 96/00102. These devices and methods do not teach forming a stent from the fluent material.
Despite the numerous stents and stent delivery devices which have been developed to date, a need still exists for a stent which can be delivered and positioned with a minimum of trauma to vascular tissue which has already been damaged by angioplasty. There is also a need for a new type of stent which can be introduced to a target site in vascular lumen substantially without trauma and without contaminating the target site or any lesion with thrombogenic material which would cause restenosis. There is also a need for an improved stent which once placed in the vascular lumen can prevent restenosis and at the same time not create a permanent danger to the patient in the event the stent is dislodged. Also needed is a stent and a method for delivering the stent which can be considerably downsized over what is presently available and which can be delivered to a target site without injury to the delicate, single layer of cells constituting the endothelial lining.